Abstract

We have investigated students' qualitative understanding of dc circuits containing resistors and a capacitor. We found that a year after traditional lecture instruction as part of an introductory physics course, most students were unable to predict the behavior of a series circuit consisting of a battery, a bulb, and a capacitor. Among the difficulties identified we found that almost half of the students implicitly abandoned the idea that a complete circuit is necessary for a bulb to light when a capacitor is introduced into the circuit. We have developed curriculum that enables students to construct a phenomenological model in which they liken the behavior of a capacitor to that of a wire, a switch, and a battery; this allows them to qualitatively describe circuits with batteries, bulbs, and capacitors. We have also developed curriculum on the determination of RC times. Post-test results show a significant increase in understanding of capacitive circuits.

Received 27 May 2012Accepted 04 March 2013Published online 16 April 2013

Acknowledgments:

This work was supported by the Irish Research Council for Science Engineering and Technology, Dublin City University's Learning Innovation Unit, and the School of Physical Sciences. The authors gratefully acknowledge fruitful discussions with Thomas Wemyss (Dublin City University), John Thompson and MacKenzie Stetzer (University of Maine), Scott McDonald (Pennsylvania State University), and Peter Shaffer (University of Washington). The authors are also grateful to Roger Feeley (University of Maine) for using the curriculum in his institution and for very useful feedback.